The invention disclosed herein is generally related to heat exchangers. More particularly, the present invention is directed to a heat exchanger suitable for use in a Stirling engine having a liquid as the working fluid.
In a Stirling engine there is a working fluid, typically a gas, which is passed through a cyclical sequence of steps in the course of converting heat to work. In one step of the Stirling cycle, the gas is compressed and passed through a heat exchanger to be cooled. In another step of the cycle the gas is expanded and passed through a second heat exchanger to be heated.
The applicants have sought to develop a Stirling engine in which the working fluid is a liquid. In such an engine the compression and expansion stages of the Stirling cycle involve much higher pressure changes and much smaller volume changes than occur in a gas-based engine. A heat exchanger suitable for such a liquid-based Stirling engine must meet several requirements. First, the total volume of fluid entrained in the heat exchanger should be small, i.e., the heat exchanger should have a small "dead volume". Secondly, the heat exchanger must have a high heat transfer coefficient. Further, the heat exchanger should have a low fluid flow impedance and a correspondingly low rate of viscous heat dissipation. Finally, the heat exchanger must be capable of accommodating liquids at variable pressures as high as several thousand pounds per square inch (psi).